Participation in regular physical activity (PA) is related to reduced all cause morbidity and mortality in older adults, in particular that caused by cardiac events and cardiovascular disease. However, objective monitoring of PA suggests that fewer than 3% of adults over age 60 meet PA recommendations. Thus it is important to develop and evaluate interventions that promote PA for older adults. Ecological models posit that behavioral interventions are most effective when they operate on multiple levels including individual, interpersonal, environment and policy. Many older adults live in Continuing Care Retirement Communities (CCRCs) and these settings provide an excellent environment in which to deliver and evaluate PA interventions that are based upon this ecological approach. Our pilot work has found that CCRC residents are mostly sedentary, highly influenced by their environment, and in need of encouragement and support to be more physically active. Most CCRCs have local management structures that provide opportunities for policy advocacy to improve social and built environments for PA and walking. This study will test the efficacy of a 6-month multilevel PA intervention, MIPARC (Multilevel Intervention for PA in Retirement Communities), using a group randomized controlled design. MIPARC will be compared to a successful aging educational attention control condition in 320 sedentary (daily step count between 1000- 5000 steps) older adult (>65 years) residents of 16 CCRCs in San Diego. MIPARC includes individual components (pedometer based self monitoring, educational materials and tailored monthly counseling calls), interpersonal components (monthly group sessions and peer mentoring), environmental components (walking signage prompts, tailored walking maps, posted step counts, and PA resource enumeration), and policy components (review of onsite activity opportunities and walkability, recommendations for change, and peer led advocacy). Our Primary Aim is to test the hypothesis that sedentary residents living in retirement communities who receive the 6-month MIPARC intervention will significantly increase their minutes of light and moderate intensity PA (measured by 7-day accelerometry) compared to the control condition. Our Secondary Aim is to test the hypothesis that, compared to the control condition MIPARC significantly improves blood pressure, physical activity performance and quality of life. Exploratory Aims will examine the impact of MIPARC on individual, interpersonal, environmental, and policy mediators and moderators of PA. Process measures collected for 12 months will be used to examine the fidelity of MIPARC implementation during the main trial, whether it is sustained for the 6-month post-intervention period and whether continued effects on PA are seen during this latter period. Mixed model analyses will be employed to account for the nested design, with site as a random effect. To our knowledge, this study will be the first to assess a multilevel ecological intervention to promote PA in older adults living in CCRCs.